Liquid ejecting apparatus and cartridge

ABSTRACT

A liquid ejecting apparatus includes an ejection portion and a circuit. The ejection portion has a plurality of ejection ports configured to eject liquid supplied from a liquid storage portion defining a liquid storage space configured to store liquid. The circuit is electrically connected to at least one of a bottom electrode and a side electrode. 
     The circuit is configured to detect a capacitance between the bottom electrode and the side electrode. The bottom electrode is provided at a bottom surface of the liquid storage portion. The side electrode is provided at one side surface of the liquid storage portion and electrically isolated from the bottom electrode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from Japanese Patent Application No.2016-212612 filed Oct. 31, 2016. The entire content of the priorityapplication is incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to a liquid ejecting apparatus which includes anejection portion having a plurality of ports for ejecting liquid and acircuit for measuring a capacitance between electrodes. This disclosurealso relates to a cartridge mountable on the liquid ejecting apparatus.

BACKGROUND

It is known to measure the remaining amount of ink in a cartridge byproviding an electrode on each of a pair of side surfaces facing eachother of a cartridge tank (i.e. a liquid storage portion), and thenmeasuring a capacitance between the electrodes.

SUMMARY

According to one aspect, this specification discloses a liquid ejectingapparatus. The liquid ejecting apparatus includes an ejection portionand a circuit. The ejection portion has a plurality of ejection portsconfigured to eject liquid supplied from a liquid storage portiondefining a liquid storage space configured to store liquid. The circuitis electrically connected to at least one of a bottom electrode and aside electrode. The circuit is configured to detect a capacitancebetween the bottom electrode and the side electrode. The bottomelectrode is provided at a bottom surface of the liquid storage portion.The side electrode is provided at one side surface of the liquid storageportion and electrically isolated from the bottom electrode.

According to another aspect, this specification also discloses acartridge configured to be mounted on a liquid ejecting apparatusincluding an ejection portion having a plurality of ejection portsconfigured to eject liquid and a circuit configured to detect acapacitance between electrodes. The cartridge includes a liquid storageportion, a bottom electrode, and a side electrode. The liquid storageportion defines a liquid storage space configured to store liquidsupplied to the ejection portion. The bottom electrode is provided at abottom surface of the liquid storage portion. The side electrode isprovided at one side surface of the liquid storage portion andelectrically isolated from the bottom electrode. When the cartridge ismounted on the liquid ejecting apparatus, at least one of the bottomelectrode and the side electrode is electrically connected to thecircuit, and a capacitance between the bottom electrode and the sideelectrode is detected by the circuit.

According to still another aspect, this specification also discloses aliquid ejecting apparatus. The liquid ejecting apparatus includes aliquid storage portion, an ejection portion, a bottom electrode, a sideelectrode, and a circuit. The liquid storage portion defines a liquidstorage space configured to store liquid. The ejection portion has aplurality of ejection ports configured to eject liquid supplied from theliquid storage portion. The bottom electrode is provided at a bottomsurface of the liquid storage portion. The side electrode is provided atone side surface of the liquid storage portion and electrically isolatedfrom the bottom electrode. The circuit is electrically connected to atleast one of the bottom electrode and the side electrode. The circuit isconfigured to detect a capacitance between the bottom electrode and theside electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments in accordance with this disclosure will be described indetail with reference to the following figures wherein:

FIG. 1 is a plan view of a printer according to an embodiment;

FIG. 2 is a cross-sectional view of a head of the printer according tothe embodiment;

FIG. 3 is a side view of the head, a sub-tank, and a cartridge of theprinter according to the embodiment;

FIG. 4 is a side view of a sub-tank unit of the printer, as viewed froma downstream side in a conveyance direction, according to theembodiment;

FIG. 5 is a cross-sectional view taken along line V-V of FIG. 3;

FIG. 6 is a block diagram showing an electric structure of the printeraccording to the embodiment;

FIG. 7 is a graph showing a relation between a remaining amount and acapacitance of both of examples of this disclosure and comparativeexamples; and

FIG. 8 is a graph showing a relation between a remaining amount and acapacitance of a plurality of examples of this disclosure.

DETAILED DESCRIPTION

When providing an electrode on each of a pair of side surfaces facingeach other of the liquid storage portion as above, if the distancebetween the electrodes becomes shorter, the capacitance becomes larger.This results in improvement of detection accuracy of the remainingamount of ink. However, in order to secure the liquid storage space,there is a limit to improve accuracy of the remaining amount byshortening distance between the electrodes.

In addition, when providing an electrode on each of a pair of sidesurfaces facing each other of the liquid storage portion as above, therate of change of the capacitance to the remaining amount is linear. Insuch a case, the detection accuracy of the remaining amount in avicinity of the empty level cannot be improved.

In view of the foregoing, an example of an object of this disclosure isto provide a liquid ejecting apparatus and a cartridge which improvedetection accuracy of the remaining amount of ink in the vicinity of theempty level.

An aspect of this disclosure will be described while referring to theaccompanying drawings. As shown in FIG. 1, a printer 1 according to oneembodiment of this disclosure has a housing 1 x. Inside the housing 1 x,there is provided an ejection unit 10, a conveyance unit 20, a cartridgeunit 40, and a control unit 50.

The cartridge unit 40 includes four ink cartridges: 40B, 40Y, 40C, 40M,each containing black ink, yellow ink, cyan ink, and magenta ink. Thefour cartridges 40B, 40Y, 40C, 40M is individually detachably mounted onthe housing 1 x.

The ejection unit 10 includes a carriage 11, a head 12 and a sub-tankunit 13 respectively mounted on the carriage 11.

The carriage 11 is supported by two guide shafts 11 g extending in thescanning direction. When the endless belt 11 b travels with driving of acarriage motor 11 m, the carriage 11 reciprocates in the scanningdirection.

As shown in FIG. 2, the head 12 includes a channel unit 12 m and anactuator unit 12 n.

The lower surface of the channel unit 12 m is an ejection surface 12 ahaving a plurality of ejection ports 12 x. As shown in FIG. 1, theejection ports 12 x form four rows of ejection ports 12B, 12Y, 12C, 12Min the conveyance direction. The four rows of ejection ports 12B, 12Y,12C, 12M are arranged side by side in the scanning direction, each ofthese rows is formed by a plurality of ejection ports 12 x ejectingsingle color ink of black, yellow, cyan, or magenta, respectively.

As shown in FIG. 2, the channel unit 12 m includes a common channel 12 yfor each color of the rows of ejection ports 12B, 12Y, 12C, 12M andindividual channels 12 z for each of the ejection ports 12 x. Theindividual channel 12 z is a channel formed from an exit of the commonchannel 12 y of a corresponding color to the ejection port 12 x via apressure chamber 12 z 1. There is a plurality of the pressure chambers12 z 1 opening in the upper surface of the channel unit 12 m.

The actuator unit 12 n includes: a vibration plate 12 n 1 provided overthe channel unit 12 m to cover the plurality of pressure chamber 12 z 1,a piezoelectric layer 12 n 2 provided over the vibration plate 12 n 1,and a plurality of individual electrodes 12 n 3 provided over thepiezoelectric layer 12 n 2 so as to face each of the pressure chamber 12z 1. A part of the vibration plate 12 n 1 and the piezoelectric layer 12n 2 in the area sandwiched between each individual electrode 12 n 3 andeach pressure chamber 12 z 1 functions as an individual unimorph typeactuator for each pressure chamber 12 z 1. This part is deformable inresponse to the voltage application by a head driver 12 d to theindividual electrode 12 n 3. When the actuator deforms to be convextoward the pressure chamber 12 z 1, the volume of the pressure chamber12 z 1 decreases and the pressure within the pressure chamber 12 z 1 isapplied to the ink therein, which results in ejection of ink from theejection port 12 x.

As shown in FIG. 1, the sub-tank unit 13 includes four sub-tanks 13B,13Y, 13C, 13M, each stores black ink, yellow ink, cyan ink, and magentaink. Each of the four sub-tanks 13B, 13Y, 13C, 13M is connected to eachof the four cartridges of corresponding color 40B, 40Y, 40C, 40M throughflexible tubes 15B, 15Y, 15C, 15M of corresponding color.

The four sub-tanks 13B, 13Y, 13C, 13M have the same configuration. Thefour cartridges 40B, 40Y, 40C, 40M have the same configuration.

As shown in FIG. 3, each of the sub-tanks 13B, 13Y, 13C, 13M has ahousing 13 x. Each of the cartridges 40B, 40Y, 40C, 40M also has ahousing 40 x. Each of these housings 13 x, 40 x is a substantiallyrectangular parallelepiped shape and defines an ink storage space 13 v,40 v for storing ink therein.

The ink storage spaces 40 v of the respective cartridges 40B, 40Y, 40C,40M communicate with the ink storage spaces 13 v of the sub-tanks 13B,13Y, 13C, 13M of corresponding color through the tubes 15B, 15Y, 15C,15M of corresponding color. The ink storage spaces 13 v of therespective sub-tanks 13B, 13Y, 13C, 13M communicate with the commonchannels 12 y of corresponding color in the head 12 through joints 16 ofcorresponding color.

The ink supplied from the ink storage space 40 v of each cartridge 40B,40Y, 40C, 40M to the ink storage space 13 v of the sub-tank 13B, 13Y,13C, 13M through the tube 15B, 15Y, 15C, 15M is temporarily stored inthe ink storage spaces 13 v and then supplied to the head 12 through thejoint 16.

As shown in FIG. 4, the housings 13 x of the four sub-tanks 13B, 13Y,13C, 13M are arranged in the scanning direction (a particulardirection).

As shown in FIGS. 3 and 4, the sub-tank unit 13 is provided with abottom electrode 3 a, four side electrodes 3 b, and four side electrodes3 c. Each side electrode 3 b is not electrically connected to (that is,electrically isolated from) the bottom electrode 3 a. In other word,there is no electrical conduction between each side electrode 3 b andthe bottom electrode 3 a. Each side electrode 3 c is electricallyconnected to the bottom electrode 3 a, and is not electrically connectedto the side electrode 3 b. The bottom electrode 3 a and the four sideelectrodes 3 c are held at a ground potential.

The bottom electrode 3 a is provided at a bottom surface 13 xa of thehousings 13 x of the four sub-tanks 13B, 13Y, 13C, 13M. As shown in FIG.4, the bottom electrode 3 a extends in the scanning direction and is acommon electrode for the four sub-tanks 13B, 13Y, 13C, 13M. The bottomelectrode 3 a faces substantially an entire region of the ink storagespaces 13 v of the four sub-tanks 13B, 13Y, 13C, 13M in the verticaldirection.

The four side electrodes 3 b are arranged at intervals in the scanningdirection on a board (substrate) 3 x provided at a side surface 13 xb ofthe housing 13 x of the four sub-tanks 13B, 13Y, 13C, 13M. The four sideelectrodes 3 b are individual electrodes for each of the four sub-tanks13B, 13Y, 13C, 13M, and are electrically connected to a capacitancemeasurement circuit for sub-tank 13 s (refer to FIG. 6). The four sideelectrodes 3 b respectively faces, in the conveyance direction, the inkstorage space 13 v of the housing 13 x of corresponding sub-tanks 13B,13Y, 13C, 13M, but does not face, in the conveyance direction, the inkstorage space 13 v of the housing 13 x adjacent to the correspondinghousing 13 x in the scanning direction. That is, each of the sideelectrodes 3 b does not face the ink storage space 13 v of the housing13 x adjacent to the housing 13 x facing the corresponding sideelectrode 3 b.

A ground electrode 3 d is arranged between the two side electrodes 3 badjacent to each other in the scanning direction. Each ground electrode3 d extends in the vertical direction and is arranged in a verticalregion substantially the same as that of the two side electrodes 3 bsandwiching the ground electrode 3 d in the scanning direction. In otherwords, each ground electrode 3 d and the two side electrodes 3 bsandwiching the ground electrode 3 d in the scanning direction aresubstantially matching each other in the vertical direction.

In the housing 13 x of sub-tanks 13B, 13Y, 13C, 13M, each of the fourside electrodes 3 c is provided at a side surface 13 xc facing the sidesurface 13 xb in the conveyance direction. The side electrodes 3 c arearranged at intervals in the scanning direction in the same manner asthe side electrodes 3 b. The side electrode 3 c faces the ink storagespace 13 v, in the conveyance direction, of one corresponding housing 13x out of the housings 13 x of the four sub-tanks 13B, 13Y, 13C, 13M. Theside electrode 3 c does not face, in the conveyance direction, the inkstorage spaces 13 v of the housings 13 x adjacent to the correspondinghousing 13 x in the scanning direction. The side electrode 3 c and theside electrode 3 b sandwich the corresponding ink storage space 13 v inthe conveyance direction.

As shown in FIG. 3, the side surface 13 xb is parallel to the verticaland scanning directions. On the other hand, the bottom surface 13 xa isslanted relative to the horizontal direction so as to be lower towardthe downstream side in the conveyance direction, i.e. the direction fromthe side surface 13 xc to the side surface 13 xb. Due to this, an angleθ1 (theta 1) formed by the bottom surface 13 xa and the side surface 13xb is an acute angle. An end portion of the bottom surface 13 xaadjacent to the side surface 13 xb (i.e. the right end of the bottomsurface 13 xa in FIG. 3) is slanted relative to the horizontal directionand forms an acute angle with the side surface 13 xb.

In the same manner as above, the side electrode 3 b is parallel to thevertical and scanning direction. On the other hand, the bottom electrode3 a is slanted relative to the horizontal direction so as to be lowertoward the downstream side in the conveyance direction, i.e. thedirection from the side electrode 3 c to the side electrode 3 b. An endportion of the bottom electrode 3 a adjacent to the side electrode 3 b(i.e. the right end of the bottom electrode 3 a in FIG. 3) is providedat the above-mentioned end portion of the bottom surface 13 xa. The endportion of the bottom electrode 3 a forms an acute angle with a surfacethat is parallel to the side electrode 3 b and that extends upward fromthe tip end of the end portion of the bottom electrode 3 a.

A lower end 3 b 1 of each side electrode 3 b is located at a higherposition than a lower end 13 v 1 of the corresponding ink storage space13 v.

As shown in FIG. 5, the four cartridges 40B, 40Y, 40C, 40M aredetachably mounted on respective ones of four storing chambers 1 zprovided in a cartridge holder 1 y. The four storing chambers 1 z arearranged in the scanning direction. Thus, when the four cartridges 40B,40Y, 40C, 40M are mounted on the printer 1, the housings 40 x of thesecartridges are also arranged in the scanning direction.

As shown in FIGS. 3 and 5, each of the cartridges 40B, 40Y, 40C, 40M isprovided with a bottom electrode 4 a, a side electrode 4 b, and a sideelectrode 4 c. The bottom electrode 4 a, the side electrode 4 b, and theside electrode 4 c are individual electrodes with respect to eachcartridge 40B, 40Y, 40C, 40M. In each of the cartridges 40B, 40Y, 40C,40M, the side electrode 4 b is not electrically connected to the bottomelectrode 4 a. The side electrode 4 c is electrically connected to thebottom electrode 4 a, but is not electrically connected to (that is,electrically isolated from) the side electrode 4 b.

The bottom electrode 4 a is provided at a bottom surface 40 xa of thehousing 40 x of each cartridge 40B, 40Y, 40C, 40M. The bottom electrode4 a faces substantially an entire region of the ink storage space 40 vof the corresponding one of the cartridges 40B, 40Y, 40C, 40M.

The electrode 4 b is provided at a side surface 40 xb of the housing 40of each cartridge 40B, 40Y, 40C, 40M.

In the housing 40 x of each cartridge 40B, 40Y, 40C, 40M, the sideelectrode 4 c is provided at a side surface 40 xc facing the sidesurface 40 xb in the scanning direction. The side electrodes 4 b and 4 csandwich the corresponding ink storage space 40 v in the scanningdirection.

Terminals 40 s 1, 40 s 2 are provided at bottom and side walls whichdefine each storing chamber 1 z in the cartridge holder 1 y. Theterminal 40 s 1 is held at a ground potential and the terminal 40 s 2 iselectrically connected to a capacitance measurement circuit forcartridge 40 s (refer to FIG. 6.). When cartridges 40B, 40Y, 40C, 40Mare mounted in the storing chamber 1 z, the terminal 40 s 1 contacts thebottom electrodes 4 a and the terminal 40 s 2 contacts the sideelectrode 4 b, so that the bottom electrode 4 a is held at a groundpotential, and the side electrode 4 b is electrically connected to acapacitance measurement circuit for cartridge 40 s.

As shown in FIG. 5, the side surface 40 xb is parallel to the verticaland conveyance directions, while the bottom surface 40 xa is curved tobe convex upward. Because of this, an angle θ2 (theta 2) formed by anend portion of the bottom surface 40 xa adjacent to the side surface 40xb (i.e. the left end of the bottom surface 40 xa in FIG. 5) and theside surface 40 xb is an acute angle. In other words, theabove-described end portion of the bottom surface 40 xa is slantedrelative to the horizontal direction and forms an acute angle with theside surface 40 xb.

In the same manner as above, the side electrode 4 b is parallel to thevertical and conveyance directions, while the bottom electrode 4 a iscurved to be convex upward. Because of this, an end portion in thebottom electrode 4 a adjacent to the side electrode 4 b (i.e. the leftend in FIG. 5) is provided at the above-described end portion of thebottom surface 40 xa and forms an acute angle with a surface that isparallel to the side electrode 4 b and that extends upward from the tipend of the above-described end portion of the bottom electrode 4 a.

A lower end 4 b 1 of the side electrode 4 b is located at a higherposition than a lower end 40 v 1 of the corresponding ink storage space40 v.

As shown in FIG. 1, the conveyance unit 20 conveys paper 100 in theconveyance direction. The conveyance unit 20 includes: a pair ofconveyance rollers 21 arranged at the upstream side from the head 12 inthe conveyance direction; and a pair of conveyance rollers 22 arrangedat the downstream side from the head 12. The pair of conveyance rollers21 and 22 respectively includes a driving roller and a driven rollerwhich are arranged to nip the paper 100. When the driving roller rotatesby a conveyance motor 20 m (refer to FIG. 6), the driving roller and thedriven roller rotate in opposite directions to each other.

An image is formed on the paper 100 conveyed by the conveyance unit 20in the conveyance direction with the ink ejected from the ejection port12 x of the head 12 reciprocating in the scanning direction togetherwith the carriage 11.

The control unit 50 controls each part of the printer 1. As shown inFIG. 6, the control unit 50 includes a CPU (Central Processing Unit) 51,a ROM (Read Only Memory) 52, and a RAM (Random Access Memory) 53. TheCPU 51 controls the carriage motor 11 m, the head driver 12 d, and theconveyance motor 20 m, in order to record an image on the paper 100based on an image data transmitted from an external device (for example,a PC connected to the printer 1). The ROM 52 stores programs to beexecuted by the CPU 51, various fixed data, and the like. The RAM 53temporarily stores data necessary for the CPU 51 to execute programs,such as image data.

The capacitance measurement circuit for sub-tank 13 s measures acapacitance between the bottom electrode 3 a and each side electrode 3b. The capacitance measurement circuit for sub-tank 13 s applies a sinewave to each of the side electrodes 3 b and transmits signals indicatingvoltage according to the magnitude of the above-described capacitance tothe control unit 50. The capacitance between the bottom electrode 3 aand each of the side electrodes 3 b varies depending on the remainingamount of ink in the sub-tank. The ROM 52 stores data showingcorrelation of the remaining amount of ink in the sub-tank and thecapacitance between the bottom electrode 3 a and each side electrode 3 b(a first correlation). The CPU 51 determines the remaining amount of inkin each sub-tank 13B, 13Y, 13C, 13M based on data showing the firstcorrelation stored in the ROM 52 and the signal received from thecapacitance measurement circuit for sub-tank 13 s, and executes suitableprocessing such as alarming for requesting exchange of the cartridges40B, 40Y, 40C, 40M.

The capacitance measurement circuit for cartridge 40 s measures acapacitance between the bottom electrode 4 a and the side electrode 4 bof each of the cartridges 40B, 40Y, 40C, 40M. The capacitancemeasurement circuit for cartridge 40 s applies a sine wave to each ofthe side electrodes 4 b through the terminal 40 s 2 and transmitssignals indicating voltage according to the magnitude of theabove-described capacitance to the control unit 50. The capacitancebetween the bottom electrode 4 a and the side electrode 4 b variesdepending on the remaining amount of ink in the cartridges. The ROM 52stores data showing correlation of the remaining amount of ink in thecartridge and the capacitance between the bottom electrode 4 a and theside electrode 4 b (a second correlation). The CPU 51 determines theremaining amount of ink in each cartridge based on the data of thesecond correlation and the signals received from the capacitancemeasurement circuit for cartridge 40 s, and executes suitable processingsuch as alarming for requesting exchange of the cartridges 40B, 40Y,40C, 40M.

As described above, according to the embodiment, in each sub-tank 13B,13Y, 13C, 13M, the capacitance between the electrodes 3 a and 3 b ismeasured by providing an electrode (the bottom electrode 3 a and theside electrode 3 b) on each of the bottom surface 13 xa and the sidesurface 13 xb of the housing 13 x, not by providing an electrode on eachof a pair of side surfaces of the housing 13 x facing each other. Inaddition, in each cartridge 40B, 40Y, 40C, 40M, the capacitance betweenthese electrodes 4 a and 4 b is measured by providing an electrode (thebottom electrode 4 a and the side electrode 4 b) on the bottom surface40 xa and the side surface 40 xb of the housing 40 x (refer to FIG. 3),not by providing an electrode on each of a pair of side surfaces of thehousing 40 x facing each other. Thus, as shown in the below-describedexamples, as the rate of change of the capacitance to the remainingamount becomes larger in the vicinity of empty level, the detectionaccuracy of the remaining amount of ink can be improved.

In each sub-tank 13B, 13Y, 13C, 13M, an end portion in the bottomsurface 13 xa (i.e. the right end of the bottom surface 13 xa in FIG. 3)adjacent to the side surface 13 xb is slanted relative to the horizontaldirection, and forms an acute angle with the side surface 13 xb. The endportion of the bottom electrode 3 a (i.e. the right end of the bottomelectrode 13 a in FIG. 3) adjacent to the side electrode 3 b is providedat the above-described end portion of the bottom surface 13 xa. The endportion of the bottom electrode 3 a forms an acute angle with a surfacethat is parallel to the side electrode 3 b and that extends upward fromthe tip end of the above-described end portion of the bottom electrode 3a. In each cartridge 40B, 40Y, 40C, 40M, an end portion of the bottomsurface 40 xa (i.e. the left end of the bottom surface 40 xa) adjacentto the side surface 40 xb is slanted relative to the horizontaldirection and forms an acute angle with the side surface 40 xb. The endportion of the bottom electrode 4 a (i.e. the left end of the bottomelectrode 4 a in FIG. 5) adjacent to the side electrode 4 b is providedat the above-described end portion of the bottom surface 40 xb, andforms an acute angle with a surface that is parallel to the sideelectrode 4 b and that extends upward from the tip end of theabove-described end portion of the bottom electrode 4 a. In this case,as shown in the below-described examples, the capacitance becomes largerin a region where the remaining amount is relatively large, comparedwith a case where a bottom surface is not slanted relative to thehorizontal direction and a bottom electrode and a side electrode areperpendicular to each other. This suppresses enlarging the electrode forsecuring a capacitance required for detection of the remaining amount,and the electrodes and related components such as boards can bedownsized. Moreover, as shown in the below-described example, the rateof change of the capacitance to the remaining amount becomes larger inthe vicinity of empty level, compared with a case where a bottom surfaceis not slanted relative to the horizontal direction and a bottomelectrode and a side electrode are perpendicular to each other. Thus,the detection accuracy of the remaining amount of ink can be improved.

In each sub-tank 13B, 13Y, 13C, 13M, the lower end 3 b 1 of the sideelectrode 3 b is located above the lower end 13 v 1 of the correspondingink storage space 13 v (refer to FIG. 3). In each cartridge 40B, 40Y,40C, 40M, the lower end 4 b 1 of the side electrode 4 b is located abovethe lower end 40 v 1 of the corresponding ink storage space 40 v (referto FIG. 5). In this case, before the liquid level reaches the lower ends13 v 1, 40 v 1 of the ink storage space 13 v, 40 v, in other words,before reaching the empty level, the capacitance rapidly approaches nearzero at the phase when the liquid level reaches the lower ends 3 b 1, 4b 1 of the side electrodes 3 b, 4 b. Accordingly, the detection accuracyof the remaining amount of ink can be improved in the vicinity of empty.

The housings 13 x for the sub-tanks 13B, 13Y, 13C, 13M are arranged inthe scanning direction (refer to FIG. 4). The bottom electrode 3 aextends in the scanning direction (i.e. parallel to the arrangement ofthe four housings 13 x), and the single bottom electrode 3 a is a commonelectrode for the four housings 13 x. The side electrode 3 b is anindividual electrode for each of the housings 13 x. In this case, ifeither one of the bottom electrode 3 a and the side electrode 3 bextends along the arrangement direction of the four housings 13 x, sucha common electrode can be easily formed. In addition, the use of thecommon electrode makes wiring for each electrode unnecessary, therebyfacilitating manufacturing of the sub-tanks 13B, 13Y, 13C, 13M anddownsizing the components around the electrodes.

The four side electrodes 3 b are arranged on a single board (substrate)3 x in the scanning direction (i.e. the arrangement direction of thefour housings 13 x) (refer to FIG. 4). This configuration suppressescomplexity of wiring and facilitates the manufacturing, compared withthe case of providing the individual electrode on an individual board.

Each of the four side electrodes 3 b does not face the ink storage space13 v of the housing 13 x adjacent to the housing corresponding to thatside electrode 3 b among the housings 13 x of the four sub-tanks 13B,13Y, 13C, 13M (refer to FIG. 4). Thus, in detecting the remaining amountof each sub-tank 13B, 13Y, 13C, 13M, a problem of being affected by aninfluence of the remaining amount of adjacent sub-tanks can besuppressed.

The ground electrode 3 d is provided between the adjacent two sideelectrodes 3 b, 3 b (refer to FIG. 4). The ground electrode 3 dsuppresses an influence of the remaining amount of ink in the adjacentsub-tank during the detection of the remaining amount in each sub-tank13B, 13Y, 13C, 13M.

In the sub-tank 13B, 13Y, 13C, 13M, another side electrode 3 c which iselectrically connected to the bottom electrode 3 a but not electricallyconnected to the side electrode 3 b is provided at one side surface 13xc, among the plurality of side surfaces of the housing 13 x, facing theside surface 13 xb on which the side electrode 3 b is provided (refer toFIG. 3). In the cartridges 40B, 40Y, 40C, 40M, another side electrode 4c which is electrically connected to the bottom electrode 4 a but notelectrically connected to the side electrode 4 b is provided at one sidesurface 40 xc, among the plurality of side surfaces of the housing 40 x,facing the side surface 40 xb on which the side electrode 4 b isprovided (refer to FIG. 5). As shown in the below-described example,this increases the rate of change of the capacitance to the remainingamount of ink in the region having a relatively large remaining amount,thereby improving the detection accuracy of the remaining amount,compared with the case where the other side electrodes 3 c and 4 c arenot provided.

Hereinafter, analysis results will be described with reference to FIGS.7 and 8, regarding a relation between the remaining amount of ink andthe capacitance in examples of this disclosure and comparative examples.The arrangement of electrodes in one liquid storage portion is differentin each example.

In Example 1 of this disclosure, the bottom electrodes (i.e. the bottomelectrodes 3 a, 4 a of the above embodiment) and the side electrodes(i.e. the side electrodes 3 b, 4 b of the above embodiment) are arrangedon a rectangular parallelepiped liquid storage portion (i.e. having noslant or curve in the bottom and side surfaces), without providing theother side electrodes (i.e. the side electrodes 3 c, 4 c in theabove-described embodiment).

In Example 2 of this disclosure, the bottom electrodes (i.e. the bottomelectrodes 3 a, 4 a of the above embodiment), the side electrodes (i.e.the side electrodes 3 b, 4 b of the above embodiment), and the otherside electrodes (i.e. the side electrodes 3 c, 4 c in theabove-described embodiment) are arranged on a rectangular parallelepipedliquid storage portion (i.e. having no slant or curve in the bottom andside surfaces).

In Example 3 of this disclosure, the bottom electrode (i.e. the bottomelectrode 3 a of the above embodiment) and the side electrode (i.e. theside electrode 3 b of the above embodiment) are arranged on a liquidstorage portion having a slant in the bottom surface like theabove-described sub-tank, without providing the other side electrode(i.e. the side electrode 3 c in the above-described embodiment).

In Example 4 of this disclosure, the bottom electrode (i.e. the bottomelectrode 4 a of the above embodiment) and the side electrode (i.e. theside electrode 4 b of the above embodiment) are arranged on a liquidstorage portion having a curve in the bottom surface like theabove-described cartridge, without providing the other side electrode(i.e. the side electrode 4 c in the above-described embodiment).

In comparative example 1, an electrode is arranged on each of a pair ofside surfaces facing each other in a rectangular parallelepiped liquidstorage portion (i.e. having no slant or curve in the bottom and sidesurfaces).

In comparative example 2, two electrodes are arranged side by side inthe horizontal direction on one side surface of a rectangularparallelepiped liquid storage portion (i.e. having no slant or curve inthe bottom and side surfaces).

In comparative example 3, an electrode is arranged on each of two sidesurfaces connecting to each other (intersecting each other) in arectangular parallelepiped liquid storage portion (having no slant orcurve in the bottom and side surfaces).

As shown in FIG. 7, the rate of change of the capacitance relative tothe remaining amount in Comparative examples 1-3 increasesproportionally, while the rate of change of the capacitance relative tothe remaining amount in Examples 1 and 2 of this disclosure is larger inthe vicinity of empty. Thus, it can be said that Examples 1 and 2 ofthis disclosure can improve the detection accuracy of the remainingamount in the vicinity of empty compared with Comparative examples 1-3.

FIG. 7 shows that Example 2 of this disclosure (i.e. the configurationhaving the other side electrode) has a larger rate of change of thecapacitance relative to the remaining amount than that of Example 1 ofthis disclosure (i.e. the configuration without the other sideelectrode). Thus, it can be said that, when the other side electrode isprovided, the detection accuracy of the remaining amount can be improvedin the region having a relatively large remaining amount, compared withthe configuration without the other side electrode.

FIG. 8 shows that Example 3 of this disclosure (i.e. the configurationhaving slant in the bottom surface) and Example 4 of this disclosure(i.e. the configuration having curve in the bottom surface) have alarger capacitance in the region of a relatively large remaining amount,and also have a larger rate of change of the capacitance relative to theremaining amount in the vicinity of empty, compared with Example 1 ofthis disclosure (i.e. the configuration without slant or curve in thebottom surface). Thus, it can be said that, according to Examples 3 and4 of this disclosure (i.e. a configuration where an end portion of thebottom surface adjacent to one side surface having a side electrodethereon slants relative to the horizontal direction and forms an acuteangle with the side surface; an end portion of the bottom electrodeadjacent to the side electrode is provided at the above-described endportion of the bottom surface and forms an acute angle with a surfacethat is parallel to the side electrode and that extends upward from thetip end of the end portion of the bottom electrode), the capacitance islarger in a region having a relatively large remaining amount and thedetection accuracy of the remaining amount can be improved in thevicinity of empty, compared with Example 1 of this disclosure (aconfiguration where the bottom surface is not slanted relative to thehorizontal direction and the bottom electrode and the side electrode areperpendicular).

While the disclosure has been described in detail with reference to theabove aspects thereof, it would be apparent to those skilled in the artthat various changes and modifications may be made therein withoutdeparting from the scope of the claims.

The liquid storage portion provided in the liquid ejecting apparatus isnot limited to an exchangeable tank (i.e. cartridge). The liquid storageportion may be a refillable tank to which liquid can be refilled.

The number of the liquid storage portions provided in the liquidejecting apparatus may be any number of one or more. For example, foursub-tanks (or cartridges) are used as a set in the above-describedembodiments. However, two sub-tanks (or cartridges) may be used as aset. Alternatively, only a single sub-tank and/or a single cartridge maybe provided.

When a plurality of liquid storage portions is provided in the liquidejecting apparatus, an electrode and a circuit of this disclosure may beprovided to at least one of the plurality of the liquid storageportions.

The method for measuring the capacitance by using a circuit is notlimited to the method described in the above embodiment. Any method (forexample, a bridge method, a method using a resonance frequency, a methodusing a charging time constant, and a method using a flying capacitor)may be used.

The bottom surface may not be necessarily slanted relative to thehorizontal direction, and the bottom electrode and the side electrodemay be perpendicular to each other.

The lower end of the side electrode may be located at the same height asthe lower end of the liquid storage space, or may be located at a lowerposition than the lower end of the liquid storage space.

The side electrode may be a common electrode, and the bottom electrodemay be individual electrodes.

The plurality of individual electrodes may not be necessarily arrangedon a single board.

The ground electrodes may not be necessarily provided between aplurality of individual electrodes.

The other side electrode may be omitted.

In the above-described embodiment, the bottom electrode and the sideelectrode are provided on the housing of the sub-tanks and thecartridges. Alternatively, the bottom electrode and the side electrodemay be provided on surfaces (walls) of the liquid ejecting apparatus onwhich the sub-tanks and the cartridges are arranged. That is, the bottomelectrode and the side electrode may be provided at the liquid ejectingapparatus.

For example, in FIG. 5, the bottom electrode 4 a may be provided on at abottom wall of the cartridge holder 1 y and configured to face orcontact the bottom surface 40 xa of the cartridge 40 when the cartridge40 is mounted on the cartridge holder 1 y. Similarly, the side electrode4 b may be provided on at a side wall of the cartridge holder 1 y andconfigured to face or contact the side surface 40 xb of the cartridge 40when the cartridge 40 is mounted on the cartridge holder 1 y.

The liquid stored in the liquid storage portion is not limited to ink.The liquid may be any kind of liquid (for example, a processing liquidfor agglutinating or precipitating components in ink).

This disclosure is applicable not only to a color printer but also to amonochromatic printer. This disclosure is applicable not only to aprinter but also to a facsimile machine, a photocopier, a multi-functionperipheral, and so on.

What is claimed is:
 1. A liquid ejecting apparatus comprising: anejection portion having a plurality of ejection ports configured toeject liquid supplied from a liquid storage portion defining a liquidstorage space configured to store liquid; and a circuit electricallyconnected to at least one of a bottom electrode and a side electrode,the circuit being configured to detect a capacitance between the bottomelectrode and the side electrode, the bottom electrode being provided ata bottom surface of the liquid storage portion, the side electrode beingprovided at one side surface of the liquid storage portion andelectrically isolated from the bottom electrode.
 2. The liquid ejectingapparatus according to claim 1, wherein an end portion of the bottomsurface adjacent to the one side surface is slanted relative to ahorizontal direction and forms an acute angle with the one side surface;and wherein an end portion of the bottom electrode adjacent to the sideelectrode is provided at the end portion of the bottom surface, andforms an acute angle with a surface that is parallel to the sideelectrode and that extends upward from a tip end of the end portion ofthe bottom electrode.
 3. The liquid ejecting apparatus according toclaim 1, wherein a lower end of the side electrode is located at ahigher position than a lower end of the liquid storage space.
 4. Theliquid ejecting apparatus according to claim 1, wherein the liquidstorage portion comprises a plurality of liquid storage portionsarranged in a particular direction; and wherein one of the bottomelectrode and the side electrode is a common electrode extending in theparticular direction and being common to the plurality of liquid storageportions, and another one of the bottom electrode and the side electrodeis a plurality of individual electrodes provided individually for theplurality of liquid storage portions.
 5. The liquid ejecting apparatusaccording to claim 4, wherein the plurality of individual electrodes isarranged in the particular direction on a single board.
 6. The liquidejecting apparatus according to claim 4, wherein each of the pluralityof individual electrodes does not face the liquid storage space of aliquid storage portion adjacent to a liquid storage portion facing acorresponding one of the plurality of individual electrodes.
 7. Theliquid ejecting apparatus according to claim 4, wherein a groundelectrode is provided between the plurality of individual electrodes. 8.The liquid ejecting apparatus according to claim 1, further comprisinganother side electrode provided at another side surface facing the oneside surface among a plurality of side surfaces of the liquid storageportion, the another side electrode being electrically connected to thebottom electrode and electrically isolated from the side electrode. 9.The liquid ejecting apparatus according to claim 1, further comprising:a cartridge holder for detachably mounting a cartridge thereon, thecartridge serving as the liquid storage portion; a first terminalprovided at a bottom wall of the cartridge holder and configured tocontact the bottom electrode provided on the bottom surface of thecartridge when the cartridge is mounted on the cartridge holder; and asecond terminal provided at a side wall of the cartridge holder andconfigured to contact the side electrode provided on the one sidesurface of the cartridge when the cartridge is mounted on the cartridgeholder, wherein at least one of the first terminal and the secondterminal is electrically connected to the circuit.
 10. The liquidejecting apparatus according to claim 1, further comprising: a cartridgeholder for detachably mounting a cartridge thereon, the cartridgeserving as the liquid storage portion, wherein the bottom electrode isprovided on at a bottom wall of the cartridge holder and configured toface or contact the bottom surface of the cartridge when the cartridgeis mounted on the cartridge holder; and wherein the side electrode isprovided on at a side wall of the cartridge holder and configured toface or contact the one side surface of the cartridge when the cartridgeis mounted on the cartridge holder.
 11. A cartridge configured to bemounted on a liquid ejecting apparatus including an ejection portionhaving a plurality of ejection ports configured to eject liquid and acircuit configured to detect a capacitance between electrodes, thecartridge comprising: a liquid storage portion defining a liquid storagespace configured to store liquid supplied to the ejection portion; abottom electrode provided at a bottom surface of the liquid storageportion; and a side electrode provided at one side surface of the liquidstorage portion and electrically isolated from the bottom electrode,when the cartridge is mounted on the liquid ejecting apparatus, at leastone of the bottom electrode and the side electrode being electricallyconnected to the circuit, and a capacitance between the bottom electrodeand the side electrode being detected by the circuit.
 12. The cartridgeaccording to claim 11, wherein an end portion of the bottom surfaceadjacent to the one side surface is slanted relative to a horizontaldirection and forms an acute angle with the one side surface; andwherein an end portion of the bottom electrode adjacent to the sideelectrode is provided at the end portion of the bottom surface, andforms an acute angle with a surface that is parallel to the sideelectrode and that extends upward from a tip end of the end portion ofthe bottom electrode.
 13. The cartridge according to claim 11, wherein alower end of the side electrode is located at a higher position than alower end of the liquid storage space.
 14. The cartridge according toclaim 11, further comprising another side electrode provided at anotherside surface facing the one side surface among a plurality of sidesurfaces of the liquid storage portion, the another side electrode beingelectrically connected to the bottom electrode and electrically isolatedfrom the side electrode.
 15. A liquid ejecting apparatus comprising: aliquid storage portion defining a liquid storage space configured tostore liquid; an ejection portion having a plurality of ejection portsconfigured to eject liquid supplied from the liquid storage portion; abottom electrode provided at a bottom surface of the liquid storageportion; a side electrode provided at one side surface of the liquidstorage portion and electrically isolated from the bottom electrode; anda circuit electrically connected to at least one of the bottom electrodeand the side electrode, the circuit being configured to detect acapacitance between the bottom electrode and the side electrode.
 16. Theliquid ejecting apparatus according to claim 15, wherein an end portionof the bottom surface adjacent to the one side surface is slantedrelative to a horizontal direction and forms an acute angle with the oneside surface; and wherein an end portion of the bottom electrodeadjacent to the side electrode is provided at the end portion of thebottom surface, and forms an acute angle with a surface that is parallelto the side electrode and that extends upward from a tip end of the endportion of the bottom electrode.
 17. The liquid ejecting apparatusaccording to claim 15, wherein a lower end of the side electrode islocated at a higher position than a lower end of the liquid storagespace.
 18. The liquid ejecting apparatus according to claim 15, whereinthe liquid storage portion comprises a plurality of liquid storageportions arranged in a particular direction; and wherein one of thebottom electrode and the side electrode is a common electrode extendingin the particular direction and being common to the plurality of liquidstorage portions, and another one of the bottom electrode and the sideelectrode is a plurality of individual electrodes provided individuallyfor the plurality of liquid storage portions.
 19. The liquid ejectingapparatus according to claim 15, further comprising another sideelectrode provided at another side surface facing the one side surfaceamong a plurality of side surfaces of the liquid storage portion, theanother side electrode being electrically connected to the bottomelectrode and electrically isolated from the side electrode.
 20. Theliquid ejecting apparatus according to claim 15, further comprising: acartridge holder for detachably mounting a cartridge thereon, thecartridge serving as the liquid storage portion; a first terminalprovided at a bottom wall of the cartridge holder and configured tocontact the bottom electrode provided on the bottom surface of thecartridge when the cartridge is mounted on the cartridge holder; and asecond terminal provided at a side wall of the cartridge holder andconfigured to contact the side electrode provided on the one sidesurface of the cartridge when the cartridge is mounted on the cartridgeholder, wherein at least one of the first terminal and the secondterminal is electrically connected to the circuit.